1. Field of the Invention
The present invention relates to a radio-controlled timepiece and to a control method for a radio-controlled timepiece.
2. Description of the Related Art
Radio-controlled timepieces that receive a radio signal (a longwave standard time signal) containing time data and automatically adjust and display the time based on this time data have become common in the last few years. Radio-controlled timepieces have conventionally been clocks such as mantle clocks and wall clocks, but have more recently also been rendered as wearable watches such as wristwatches.
Analog radio-controlled timepieces, however, are typically configured to detect the condition, or more specifically, the position, of the hands using a photodetector or electrical contacts, for example, and then to adjust the hands to match the received time data (see, for example, Japanese Unexamined Patent Appl. Pub. H08-179058), or are configured to adjust the hands to a predetermined time by operating the crown or push-buttons, and then to compare a count corresponding to that time with the received time data to adjust the time (see, for example, Japanese Unexamined Patent Appl. Pub. H06-258461).
The method for detecting the hand positions in Japanese Unexamined Patent Appl. Pub. H08-179058 is to render specific holes in specific gears of the movement, and detect the position of the hands by detecting the movement of these holes over the light path of a photodetector.
This configuration means that the light path of the photodetector is aligned through the thickness of the timepiece. In addition it being difficult to make the timepiece smaller with this configuration, it is also extremely difficult to render a hole in the small, precision gears that are used in a wristwatch, for example. Furthermore, the movement must be assembled so that the holes are aligned with the light path while the hands also point to a specified time. Improved manufacturability, improved productivity, and cost reductions can therefore not be achieved, and a smaller size cannot be achieved. Power is also consumed to drive the photodetector, and the usable operating time could be shortened as a result.
To achieve the time-setting operation described in Japanese Unexamined Patent Appl. Pub. H06-258461, the crown is turned to reset the hour hand, minute hand, and second hand to a predetermined time (such as 0:00:00). This resets the hour, minute, and second hand position counters to predetermined time counts corresponding to the predetermined time. At the same time, time data is input from a time data input circuit to the hour, minute, and second time counters for counting the time. The hand position counters are then incremented or decremented until the counts of the hand position counters match the counts of the time counters, and the hour hand, minute hand, and second hand are moved according to the increase or decrease in the counts to set the time.
With this method, however, the values of the hand position counters in the radio-controlled timepiece must be synchronized and initialized to the positions of the hour hand, minute hand, and second hand by resetting the hands to a predetermined time (such as 12:00). The operation for adjusting the time is therefore complicated, and the control process is also complicated due to the processing of the hour, minute, and second information.
It is therefore necessary with the conventional radio-controlled timepiece as described in Japanese Unexamined Patent Appl. Pub. H08-179058 above to render high precision holes in gears of the clock movement and to assemble the movement with high precision, thus preventing improvements in manufacturability and cost reductions, as well as preventing reductions in size due to limitations imposed by the construction. A further problem is that power consumption increases and a shortened usable time may be unavoidable.
Furthermore, with the conventional radio-controlled timepiece described in Japanese Unexamined Patent Appl. Pub. H06-258461, the values of the timekeeping counter inside the radio-controlled timepiece are synchronized to the positions of the hour, minute, and second hands to adjust the time by moving the hour hand, minute hand, and second hand to a predetermined time (such as 0:00:00) and initializing the hand position counter. As a result, all of the hands must be moved to the predetermined position. The problem is therefore that the time-adjusting operation is complicated and the control process is complex. More specifically, with most analog wristwatches the hour hand and minute hand are moved to adjust the hand positions by rotating the crown. Depending on the positions of the hands, the minute hand must therefore be turned multiple revolutions in order to move the hour hand to the predetermined position, and operation is difficult.